The texturizing of synthetic yarns, as continuous filaments, threads, tows or the like, in a stuffing chamber is commonly referred to as "stuffer-box crimping" and has been described in detail in such references as "Woven Stretch and Textured Fabrics", by Hawthrone, Interscience Publishers Division of John Wiley & Sons, N.Y. (1964), Chapter 4, pages 78-89, and more recently in "Textile Yarns" by Gosivami et al, John Wiley & Sons, N.Y. (1976), pp. 444-446. In general, the known stuffing chamber texturizing processes and apparatus feed the yarn at a high speed, e.g. by suitable nip rolls, into a confined tubular space where the yarn is compressed into a yarn plug in which the individual filament or filaments are curled, looped or folded over so as to be crimped. At or near the outlet end of the tubular space, the crimped yarn is withdrawn through a weighted tube or another braking device which restricts the tubular cross-section and places a discharge resistance on the yarn plug as it advances in the tubular space under the influence of the impinging force of the feed yarn.
The regulation of the stuffing pressure or so-called back pressure in stuffing chambers is controlled in a known manner by varying the outlet or discharge resistance of the upsetting chamber. In this case, the amount of pressure used is dependent primarily on the desired elastic properties and the voluminosity or bulk of the final texturized product. Of importance here is not only the regulatable back pressure at the outlet portion of the stuffing chamber, but also the friction of the advancing yarn plug on the interior wall surface of the stuffing chamber. Since the properties of the outer circumferential surfaces of the advancing yarn plug can fluctuate, the quality and specific characteristics of the texturized yarn may change in spite of an optimum setting of the back pressure.